Interlaced optical scanning means



March 22, 1960 F. G. wlLLEY INTERLACED OPTICAL scANNING MEANS Filed ot.19, 1954 PITCH REFERENCE T121 1. v

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SWEEP GENEAMTOR P/nw REFERENCE 65 6p 62 I VIDEO 5r 3/ ATTORNEYS UnitedStates Patent iice INTERLACED OPTICAL SCANNING MEANSvr Frank G. Willey,Roslyn Heights, N.Y., assignor to Servo `Corporation of America, NewHyde Park, N.Y., a corporation of New York Application '()ctoher 19,1954, Serial No. 463,296 13 Claims. (ci. ss-1) My invention relates toan improved optical scanning and display means and to energy-responsivemeans utilizing such opticalrscanning. The present applicationincorporates certain relinements and improvements over the inventiondisclosed in the copending patent application of Henry Blackstone andFrank G. Willey, Serial No. 320,- 272, Ytiled November 13, 1952.

It is an object of the invention to provide improved scanning means ofthe character indicated.-

' Itis another object to provide improved means for continually andautomatically scanning a field of view for varying energy levels insaid'ield.

It is a specific object to meet the above objects with amultiple-element optical scanner inherently achieving line interlace forsuccessively scanned lines.

It is a further specific object to provide display means for suitablydisplaying and for integrating the intelligence developed by successiveinterlaced scans.

It is a general object to meet the above objects with a scannerarrangement which, for certain applications, may reduce the complexityof the energy-responsive means cooperating therewith, that is, whereinthe number of channels used for indicating, amplification, and switchingmay be reduced and substantially simplified.

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred forms of the invention:

Fig. 1 is a simplified View, partly in perspective, and illustratingelements of a scanning and display device in-4 corporating features ofthe invention;

Fig. 2, is a simplified end elevation of scanner elementsof Fig. 1 Vasviewed along the axis of rotation of the scanner;

Fig. 3 is a simplified optical diagram, as .viewed substantially in theplane 3 3 of Fig. 2;

Fig.4 is a fragmentary optical and electrical diagram illustratingcomponents of a modification of the arrangement of Fig. 1;

Fig. 5 is a simplified fragmentary view of a display, representative ofscanning with the action developed by the combination of Fig. 4; and

Figs. 6 and 7 correspond to Figs. 4 and 5,Y respec-V tively, butillustrate a further modification. ,Y

Brieiiy stated, my Vinvention contemplates an improved scanner having aplurality of optical elements for causing a particular energy-responsivemeans to scan a corresponding plurality of spaced scan lines in the eldof view,

for each full revolution of the scanner. In previous ar-` rangements,all optical elements have been mountedwith their axes of opticalsymmetry in a common radial plane in which the energy-responsive meansis substantially located, but according to my new configuration, theoptical oiset imaged scan lines in the field of view, insofar as theenergy-responsive means is concerned. Arrangements are disclosed fordisplaying the video output of the energyresponsive means so as toestablish proper integration of the variously offset scan lines.Arrangements are also disclosed, whereby, for the case in which theenergyresponsive means comprises a line array of separate detectorelements, each optical element will cause the array to develop differentlines of video intelligence, appropriately interlaced to avoidduplication.

Referring to Fig. 1 of the drawings, my invention is shown inapplication to a scanner of the type described in greater detail in saidcopending patent application. Accordingly, energy-responsive means 25within a suitable capsule may be relatively flxedly mounted as by meansof a pedestal 26 on support means 27. The optical scanner may comprise adrum 28 journalled for rotation in the support means 27 (by means notshown) and continuously driven, as by a motor 29, via rim-drive means30. The scanner drum 28 may rigidly support a plurality of opticalelements which, in the form shown, are three ele ments A-B-C having likeproperties and mounted in preferably equally spaced relation about theaxis 31 of rotation of the scanner. The optical elements A--B-C may bemirrors, and the space between mirrors may be substantially equal to theangular Width of the mirrors about the axis of rotation. All mirrors maybe of the same focal length which, in the form shown, is substantiallyequal to the mirror-mounting radius about the axis of rotation 31.

As explained more fully in said copending application, the field of Viewfor any particular scan line developed on rotation of the scanner 28 maybe of the order of 60 and may require a clearance or window opening ofthe order of for a three-mirror system of the character shown. In orderto eliminate spurious responses, it is desirable to shield the scannerat 34 for all but the limits 32-33 of the window opening. The shield 34is merely shown in Fig. 1 by way of suggestion, and it will beunderstood to be mounted xedly to and effectively as a part of thesupport means 27. For certain applications, it is desirable to providefor bodily pitching or scan-depression movement of the describedscanner, and, in that event, a pitch axis 35, passing preferably throughthe central radial plane of symmetry of optical responses and preferablyperpendicular to the axis of rotation 31, will be understood to suggestprovision for this feature. I have shown at 36 a pitch-drive motor withgeared connection at 37 to the support means 27 in order to train themechanism in pitch or in scan-depression, depending upon the utilizationof the device.

Y In accordance with the invention, one full rotation of the scanner 28is caused to develop a plurality of different scan lines, all through aninherent property of the optics in the scanner. To achieve this, I somount the elements y A-B-C that they will be eccentrically offset withrespect to each other in reference to the central radial plane` ofsymmetry of scan. Stated in other words, the axes of optical symmetry ofthe focusing elements A--B-C preferably all intersect or substantiallyintersect the axis of rotation 31, but the points of these intersectionsare preferably lognitudinally spaced from each other along said axis ofrotation 31.

. The inherent function of the described arrangement will be betterunderstood by reference to Figs. 2 and 3, Fig.'3 being understood as aschematic representation of sections through the scanning mirrors A-B-Cas they successively scan theirrespectiverlines in the field of view.The mirror B is shown to have its axis 39 of Optical symmetrysubstantially in the radial plane of symmetry of scanning action andaligned with the energyresponsive element 25' contained within thecapsule 25 (Fig. v1). The mirror A is shown eccentrically mounted PienreMar. z2, leso with respect to the mirror B and with its axis 40 ofoptical symmetry offset from the radial plane in which the axis 39 islocated, but nevertheless directed generally for intersection with Jtheaxis 31 of scan rotation. The mirror C is similarly eccentricallyoffset, but in the opposite direction, so that its axis 41 of opticalsymmetry is. offset to theV side of the radial plane in which the axis39' is located. Again, the axis 41 is preferably directed forsubstantial intersection with the axis of scanned rotation 31. If thecapsule 2S should be but one energy-responsive element or indicator 25',then I prefer that the eccentric oisets of the mirrors with respect toeach other shall be such as to space the intersections of axes 39- 40-41with scan axis 31 by an amount representing one to two detector-elementwidths. For example, if they spot size achievable withy the detectorelement 25' is effectively 0.25 degree viewed through any opticalsystem, then the eccentric offsets from the central mirror B arepreferably from 0.25 to 0.5 degree, although, for certain specialpurposes, other eccentric displacements may be desirable.

In order to display properly integrated intelligence developed from thevideo-signal output of cell 25, videodisplay means may be employed, andI show cathoderay-tube display means 42 having an intensity-modulationconnection to the cell 25, via suitable signal-processing means 43,which may include one or more amplifiers. Assuming that the predominantscan lines are to be displayed horizontally across the face of the tube42, I show a horizontal sweep generator 43, with synchronized connectionat 44 to the line-scan rate. The vertical deflection rnay be governed bysuitable amplifier means 45 controlled by a step-function. generator46.V The generator 4,6 should also have a synchronized connection to theline-scan rate so that a different one of three available bias voltagesmay be applied on the vertical-deection axis for the duration of eachsuccessive scan line. The synchronization for deflection voltages shouldthus be such, for example and with reference to Fig. 3, that successivebiases will produce a first horizontally swept line scan for the opticalelement A, a second line scan for the optical element B, and a thirdline scan for the optical element C, whereupon the sweep pattern for thedisplay will repeat itself for the next rotation of scanner 28.

In airborne scanning operations, that is, operations in which my scanneris employed for scanning the terrain beneath an aircraft, thescanner-rotation axis 31 is preferably oriented with the true Hight axisof the aircraft', and the window opening 32-33 faces below the aircraftand symmetrically on opposite-sides of the vertical plane including theight axis. Usually there is no need for pitch control as by means 36,`but should there beV an adjustment in pitch, suitable pick-off means 47'may be connected, as through selector switch.48, in controllingrelationwith the amplifier' 45', thereby' controllingv the magnitude of biassteps called for by the generator 46; the scaling of bias steps thuscontrolled by means' relation on the face of the tube 42, even thoughthis may represent a plurality ofrevolutions of the scanner 28. Thisdisplacement may be achieved through' progressive depression of thevertical-deflection!bias,.scaled to'- the aircrafts velocity-altitudefunction, and maybe available from aso-called V/H meter 49, as oftheform Stone. In the event of V/H control of the display, the.`

4 selector switch 48 may vbe thrown to derive V/H rather than pitchcontrol of the deflection amplifier 4S, as will be understood.

In Figs. 4 and 5, I show applicability cf my invention tomultiple-element arrays within the energy-responsive means 25. In theform shown in Fig. 4, the elements 50-51-52-53-54 are alignedpredominantly in the direction of the axis 31 of scanner rotation andare substantially in the focal plane of mirrors A-B-C. In order thatthere shall be no overlap or duplication of lines scanned by one mirrorwith the lines scanned by a successive mirror, I prefer that therelative eccentric offsets of the axes 403941 of these mirrors shall besubstantially the effective angular width of the array 50 tc 54, as seenthrough any optical system. This will mean that the currently scannedarea seen through mirror A will effectively place the entire detectorarray on one side of the central position (of the array) and that thecurrently scanned area seen by mirror C will be correspondingly offseton the other side.

For display purposes, high-speed switching means 5'5 may rapidlycommutate the outputs of elements 50 to 54,- as amplified at 56, andasingle line 57 may relay the commutated video signal to theintensity-modulation coli-V nection for the display means (not shown).Horizontal' sweeping may be aspreviously described, and verticaldelectionwill also involve essentially the same treatment, there beingan appropriate vertical-deflection bias applied to thevertical-deflection axis for each instantaneously available element ofvideo signal, regardless of the optical system through which it is seen.Thus, a first or highspeed step-function generator 58 may operate in'synehronism with the switching sequence in means 5S, as suggestedvby aconnection 59, and a second or slow-speed step-function generator 60 mayrespond to scan synchronization, available mechanically as suggested bythe line 61 and' described in greater detail at 46 in Fig. l. Addingmeans 62 may combine the outputs of the slowspeed and high-speedstep-function generators 60-58- to achieve the desired bias coordinationon the verticaldeflection axis and, if desired, the pitch-reference orV/ H- reference control may be applied at 63 in controlling relationwith the step-function generator 60.

In operation, the slow-speed step-function generator 60 will beunderstood to establish (for each full scan-lineV duration) a givenreference bias on which the high-speed step-function output of generator58 is superposed. For. thls rst scan line then, the optical element Amay cause display on the face 63 of the cathode-ray tube of a first onthe vertical-deflection axis, so that lines labelledY 14-15-16-17--18will be developed in the display,

properly related to the lines 9-13. Similarly, forA thet thirdvand lastscan sweep of a given rotation of scanner 28, generator 60.will furtherdepress the bias on'the vertical-deflection axis, and scan lines19--20-21--22-23 will be developed, properly related to the lines 9-18.Thus, for one full rotation of the scanner 2S, the number of lines thatcanbe displayed will be a full framel orraster, representing the numberof detector elements (five) times the number of scanner elements(three).

`The arrangement of Figs. 6 and 7 is in many respectsl the same as thatdescribed for Figs. 4 and 5, the only difference beingthat theindividual energy-responsiveele-vr spaced from each other by an amountrepresenting", at

least-the-effective angular width of each energy-responsiveelement timesthe number of optical elements in the scanner. For simplification, thisspacing is shown as three timeslthe detector-element width. In order toachieve lineeinterlace for this vspacingof detector elements,.thereclcentric offsets of the respective optical elements A-B-C are relativelysmall and for the arrangement shown are preferably substantially theeffective angular width of each detector element.

The video signals for the arrangement of Fig. 6 may be processed in thesame amplifier means 56 as described for Fig. 4 and may be commutated inswitching means 55 for supply to the intensity-modulation connection ofthe display means. Since the detector-element responses represent widerspacings, however, the high-speed stepfurlction generator 58 must bevadjusted for greater bias steps; also, since the mirrors are lesseccentrically displaced from each other than in the case of Fig. 4, theslow-speed step-function generator 60 must be adjusted for relativelysmall incremental bias steps.

In operation, the device of Fig.`6 will achieve a writing of the lineslabelled A in Fig. 7 (being lines 9'-12'- '-18'-21') for the first`optical-element scan, namely, the scan by mirror A. The next successivescan will be by mirror B and will achieve display of the lines labelledB (being lines 10-13-16-19-22). Finally, the `third optical element Cwill achieve writing of the lines labelled C (being lines 11-14-17.-20-23').

While I have described eccentric offsets of optical-element axes (oreccentric mountings of optical elements) Without particular regard forspeciying angles, it will be understood that for the case of lenses thefull eccentric axis oiset is implied, whereas for the case of offsetmirrors, the predominant optical axis of the offset element need only bedisplaced one half the angle through which it is desired that thereflected image shall have been oifset; this will be understood from thenature of a mirror to reect with effectively a doubling of the angle ofincidence (i.e. angle of incidence plus angle of reiiection) for rayscollected thereby.

It will beseen that I have described a relatively simple improvementover the scanners previously referred to and that my improvement caninherently achieve lineinterlace, to complete a given raster of displayin shorter time and/or with fewer elements than heretofore possible.Reduction of the number of elements required to create a raster impliesimportant economies in amplifiers, switching complexity and the like,and there is the further advantage that the entire raster appears to theeye to have less of a ickering characteristic.

imaging said energy-responsive means in a field of View and sweeping thesame across said field on rotation of said bodily rotatable means, oneof said focusing elements having an optical axis of symmetrysubstantially aligned with said energy-responsive means, and another ofsaid focusing elements having an axis of optical symmetry eccentricallydisplaced with respect to said energy-responsive means, whereby for afull bodily rotation of said focusing elements, said energy-responsivemeans may be caused to scan a plurality of spaced scan lines in a lieldof view.

3. Optical-scanning means, comprising support means, energy-responsivemeans relatively xedly carried by said support means, a plurality oflike optical focusing elements in angularly spaced relation about saidenergyresponsive means and imaging said energy-responsive means in afield of view, and means for bodily rotating said focusing elementsabout an axis passing substantially through said energy-responsivemeans, one of said focusing elements having an axis of optical symmetryeccentrically displaced with respect to said energy-responsive means onone side of the radial plane including said energy-responsive means, anda second of said focusing elements having an axis of optical symmetryeccentrically displaced with respect to said energy-responsive means onthe other side of the radial plane, whereby the image developed by eachfocusing element may be caused to scan a different-portion of the eld ofview for each bodily rotation of said focusing elements. v

4. In an optical scanner, support means, energy-responsive meansrelatively lixedly carried by said support means, means mounted forbodily rotary displacement about said energy-responsive means and aboutan axis xed with respect to said support means, three focusing mirrorsof like focal length carried by said last-deined means in equalangularly spaced relation and imaging said energy-responsive means in afield of View, the spaces between said mirrors being substantially equalto the effective angular Width of said mirrors, the focal length of saidmirrors being substantially the mounting radius about the axis ofrotation, the axis of optical symmetry of one of said mirrors beingsubstantially in the radial Yplane including said energy-responsivemeans, the axis of optical symmetry of another of said mirrors beingeccentrically displaced on one side of said radial plane,

. and the axis of optical symmetry of lthe third of said While theinvention has been described in detail for the I preferred forms shown,it will be understood that modiications may be made without departingfrom the scope of the invention as defined in the claims which follow.

I claim:

i1. Optical-scanning means, comprising support means, energy-responsivemeans relatively fixedly carried bysaid support means, optics includinga plurality of focusing elements focused on said energy-responsive meansand imaging said energy-responsive means in a ield of view, saidfocusing elements being in angularly spaced relation and mounted forbodily rotary displacement about an axis passing substantially throughsaid energy-responsive means, each of said focusing elements having apredominant optical axis of symmetry passing through the axis ofrotation of said elements, the intercepts of said optical axes with saidaxis of rotation being longitudinally spaced with respect to each otheralong said axis of rotation, whereby for a full bodily rotation of saidelements, the respective images of said energy-responsive means due tosaid respective focusing elements may be caused to scan a plurality ofspaced scan lines in the field of view.

2. Optical-scanning means, comprising support means, energy-responsivemeans relatively xedly carried by said support means, a plurality oflike optical elements in angularly spaced relation about saidenergy-responsive means, and means for bodily rotating said focusingelements about an axis passing substantially through saidenergy-responsive means, each of said focusing elements mirrors beingeccentrically displaced on the other side of said radial plane.

5. Optical-scanning means, comprising support means, energy-responsivemeans relatively xedly carried by said support means, optics including aplurality of focusing elements focused on said energy-responsive means,said focusing elements being in angularly spaced relation and mountedfor bodily rotary displacement abou-t an axis passing substantiallythrough said energy-responsive means, said energy-responsive meansincluding a plurality of energy-responsive elements aligned in spacedrelation substantially on said axis of rotation, each of said focusingelements having a predominant optical axis of symmetry passing throughthe axis of rotation of said focusing elements, the intercepts of saidoptical axes with said axis of rotation being longitudinally spaced withrespect to each other along said axis of rotation.

6. A device according to claim 5, in which the effective eccentric olsetof said optical axes is less than the effective angular spacing of theelements of said energy-responsive means.

7. A device according to claim 6, in which the amount by which theeifective angular spacing of said Aenergyresponsive elements exceeds theoffset of adjacent optical axes is substantially a multiple of theenergy-responsive element size, said multiple corresponding to theplurality of focusing elements.

8. A device according to claim 5, in which the effective eccentricoffset of said optical axes is greater than @semana the effective-angular spacing of the elements of said energy-'responsive means.

9. A device according to claim 8, in which the' amount by which theeffective offset of adjacent optical axes exceeds the effective angularspacing of said energy-resp'o'nsive elements is substantially a multipleof the energyresponsive element size, said multiple corresponding to theplurality of said energy-responsive elements;

l0. Optical-scanning and display means, comprising a line array ofrelatively xed energy-responsivev means, a rotatable optical supportincluding a plurality of angularly spaced optical elements imaging saidenergy-responsive means in a ield of view and causing said array ofenergy-responsive means to scan a corresponding plurality of successivesets of scan lines per revolution, said optical elements beingrelatively olset with respect to each other so as to cause images ofsaid energy-responsive means to scan interlaced sets of scan linesy in aeld of view for any full rotation of said optical elements,signal-processing means including amplifier means respon; sivey to saidarray of energy-responsive means, high-speed switching means samplingthe output of said amplifier means corresponding to each element of saidarray, display means intensity-modulated by the' output of saidswitching means, and means synchrc'mizedl with operation of saidswitching means and with rotation of said optical elements for causingsuccessive'sets of intensitymodulated lines rellecting the output ofsaid amplifier means to trace sets of display lines spaced inaccordancek with the relative oisets of said optical elements.

11. Optical-scanning and display means, comprising relatively xedlymounted energy-responsive means, a scanner mounted for bodily rotationabout anv axis passing substantially through said energy-responsivemeans, optics including a plurality of angularly spaced like opticalelements carried by said scanner and imaging said energy responsivemeans on successive scan lines in a field of view, said optical elementsbeingeccentrically ofsetwithrespect to each other, whereby thesuccessive lines scanned by said energy-responsive means upon rotationof said scanner will be in spaced relation in the feldof view,cathode-ray tube display means having intensitymodulation meansconnected to said energy-responsive means, means synchronized withrotation of'said scanner for sweeping one axis of said cathode-raydisplay meansv in synchronism with successive optical scans of the iieldof View, and step-function generator means synchronized with scannerrotation for biasing the other deflection axis of said cathode-raydisplay means in steps corresponding successively to successive opticalelements of scans of the field of view.

l2. The device according to claim l1 adapted for aerial reconnaissanceand in which the axis of rotation of said scanner is substantiallyaligned with the flight axis of carrying aircraft, andvelocity-altitude-responsive means connected in controlling relationwith the magnitude of bias steps relayed by said step-function generatorto said other deiieetion axis of said cathode-ray display means.

13. A device according to claim 11,'` in which said energy-responsivemeans includes a support mounted for rotation about a pitch axis normalto the predominantV direction of the ield of view and normal to the axisof rotation of said scanner, and means responsive to orientation of saidsupport about said pitch axis and in con-A trolling relation with themagnitude of bias steps relayed by said step-function generator to saidother deflection axis of said cathode-ray display means.

References Cited in the file of this patent UNITED STATES PATENTS1,876,272 Bayer Sept. 6, 1932 2,453,502 Dimmick Nov. 9, 1948 2,553,606Rines May 22, 1951 2,668,869 Iams Feb. 9, 1954 2,709,716 Haller May 31,1955 2,779,819 Graham Ian. 29, 1957

